Boat



Aug. 20, 1935. A. J. DAWSON BOAT Filed May 5', 1934 3 Sheets-Sheet, l

INVENTOR ATTORNEY$ BOAT A. J. DAWSON Filed May 5, 1934 Aug. 20, 1935 A.J. DAWSON BOAT Filed May 5, 1934 3 Sheets-Sheet 3 INVENTOR BY 5 mid/{0Z5flu ATTORNEY5 Patented Aug. 20, 1935 STATES BOAT Albert J. Dawson,Sewickley, Pa., assignor to The Dravo Contracting Company,

Pennsylvania Application May 5, 1934, Serial No. 724,066

3 Claims.

This invention relates to boats, and particularly to tunnel boats, andconsists in an improvement in architecture, in consequence of which theboat is rendered more fully responsive to its helm, particularly whendriven astern.

The invention is illustrated in the accompanying drawings. Fig. I is aview in side elevation of a boat in which the invention is embodied.Fig. II is a fragmentary view to larger scale, showing in plan fromabove the stern portion of the boat of Fig. I, and illustratingdiagrammatically, and in association with those architectural featuresthat characterize the invention, the steering gear of the boat. Fig. IIIis a view to larger scale of the stern portion of the boat, seen invertical and medial section. From this figure the propeller has beenomitted; the skeg and rudder structure on the port side are seen in sideelevation; and, additionally, on other planes of section. the rudderstocks are shown in detail. Fig. IV is a plan view from beneath of theskeg and rudder assembly of Fig. III. Fig. V is a fragmentary view invertical and transverse section on the center line of the stock of theforward rudder element, the plane of section being that indicat d atV--V, Fig. III. From this figure, however, the rudder element itself isabsent.

The hull l of the boat illustrated is shaped at the stern with a tunnelWhose peak is indicated at 2 (Figs. I, III, and V) and within thistunnel the propeller 3 (diagrammatically indicated in Figs. I and II) isassembled, to rotate in usual manner. To such an assembly a rudder(ordinarily a double rudder) is added. And such an assembly, with theadded rudder. is effective, so far as concerns the forward travel of theboat. When, however, it comes to travel astern, the lateral thrustimparted to the boat in one direction or the other by the rotation ofthe propeller is of such relatively great magnitude, particularly inassociation with a tunneled stern, that the rudder is rendered of littleor no effect, and the direction of travel is not under adequate control.It is the object of this invention to afford adequate control of theboat in traveling astern.

In the boat of my invention the tunnel in PM stem is extended by theformation of twin e 4 that extend forward and aft and downward on eitherside of the propeller (when the propeller is in position). These skegs,so situated, serve to meet and to direct downwardly the streams of waterdelivered by the rotating propeller,the streams that, otherwise drivenlaterally, would (as in the usual construction) render the rudderrelatively ineffective.

a corporation of The skegs 4 at their fore and aft edges stand free ofthe hull; and at these edges are mounted the stocks 5 and 6 of theforward and after blades 1' and 8 of two-part rudders. As will beperceived on reference to Fig. II, the two-part rudder is duplicated, onthe port and starboard sides.

The skegs 4, together with the arch of the tunnel, constitute ashrouding that surrounds the rotating propeller on all sides, savebelow; in consequence, the transverse thrust of the rotating race of thepropeller is turned and directed downward, and, as has been said, thevessels helm is in consequence relieved of a disturbing influence.

The arrangement of skegs and rudders is such that stream flow isconfined in a fore-and-aft direction, and in consequence the angle ofattack of the rotating propeller upon the so confined water is mostefiicient.

The stocks 5 of the forward rudder blades 1 are provided with arms 9;and the stocks 6 of the after rudder blades 8 are provided with arms In;and arms 9 and ID are articulated, as indicated in Fig. II, to the endthat the whole rudder assembly shall swing as a unit, the forward andthe after blades in simultaneous and oppositely directed swing, inresponse to the movement of a steering engine I I. The steering actionproduced by the simultaneous swing of the four blades of the doublerudder is such that, for either direction of motion, the wheel-race as aunit is shifted and the direction of its extent is changed as a unit,without undue turbulence, and without reduction of propulsionefiiciency. Manifestly the forward pair of blades 1 and the after pairof blades 8 may be separately articulated, and means may be provided forswinging one pair or the other separately, or both in unison.

The skegs are shown as plane-surfaced toward the propeller. It will beunderstood that the surfaces of the skegs may be minutely modified inshape and that the width of the space defined by and between them may bevariable, decreasing and widening, in accommodation to stream-flowlines.

The rudder blades will be seen to be tapered from the stocks upon whichthey are carried to their free edges. The drawings show (Figs. II andIV) minute adjustment of the rudder blades in their relative positions.The after blades 8 of the double rudder converge slightly, to afford awheel-race of uniform width to the tips of blades 8, in consequence ofwhich the vessels response to the helm, when being propelled in theahead direction, will be increased; and, correspondingly,

E FF CE?! the forward blades 1 are adjusted in slightly divergingassembly in order to set these rudders more nearly in the line ofaverage stream-flow toward the propeller.

The elaboration of the double rudder, with two forward and two afterblades, with such interconnection as has been described, to efiectorganized and simultaneous swing, permits such a proportioningandadjustment that the forces tending to resist the swinging of the severalelements are balanced one against another, with the consequence andeffect that relatively small power is required at the helm, to swing therudder and steer the vessel.

I claim as my invention:

1. A boat of tunnel type, provided with twin skegs constituting downwardextensions of the tunnel walls, a propeller arranged in the spacebetween said skegs, and two rudder blades arranged one at the forwardand the other at the after edge of each skeg.

2. A boat of tunnel type, provided with twin skegs constituting downwardextensions of the tunnel walls, a propeller arranged in the spacebetween said skegs, two rudder stocks arranged at the forward and afterends of each of the two skegs, a rudder blade borne by each stock, andmeans for turning simultaneously the four rudder stocks in one or theother direction of turn- 3. The structure of claim 2, the wheel-racedefined by and between skegs and rudder blades 15 being wider at theforward than at the after end.

ALBERT J. DAWSON.

